OD Off is an alternative to bigger tires with stock gears. Your 285's probably measure out at 32"? 31.5"? Which puts your OD Off at 2800 or so @ 70? If you were going faster, the rpm's went up from there, so it isn't surprising that your mileage dropped. 2400-2600 is what you want to shoot for.

It's all about the setup.

 

Thanks, I was at 2800 at 75, 3000 at 80. Drove 40 miles at 78. I think I am now dead set on regearing, just need to decide on 4.88 or 5.13. I plan to stick with 33s for a while, if not for the life of the jeep, so I will prob go 4.88.

 

You drove 40 miles at 2900 rpm. Did the temperature go up at all?

 

4.88? 5.13? with 33’s? 90% highway? That’s just crazy talk! You’re going to rev the piss out of it. But it is your money.

 

You haven't really been paying attention to gearing on auto's, have you?

If you haven't found it yet, there is a good rpm chart in the faq's. - But an auto with 5.13's, and tires with an 'actual' height of 32" gives right around 2600rpm at 70. (which is real close to the rpm's on a stock manual rubicon, right?) Great for not downshifting on the freeway, and hardly reving the piss out of it. If there is absolutely no chance of moving to 35's, then 4.88's may be a better choice, though I ran the 5.13/32" setup for 6 months and had no issues at all.

 

What was your MPG during that time?

 

Can't really comment, as the only freeway driving I did was OD Off at 65 towing the boat out to the lakes, so the rpm's were up in the mid-3k's. Probably would have been fine OD On, but I'd rather burn some gas than fry a transmission.

 

So you are supposed to turn OD off when towing? Or you did not want to hunt for gears?

 

Most mfg's recommend towing heavy loads with OD Off, as it is less stress on the transmission. With that gearing and tire size, I probably would have been fine. But I was already having issues with the dealership service department over a 'towing' issue, so chose to burn gas rather than chance a transmission warranty claim.

 

Thanks, you have been extremely helpful. I found a guy locally through someone on this forum who only charges 200 per axle to regear. So it may be sooner than planned.